Crotalaria

Over 600 species of the genus Crotalaria or rattlebox exist worldwide, with the majority of them native to Africa, though there are some native to the United States.  In their native habitat, they can be found in damp grasslands, floodplains, and along the edges of rivers, swamps, and other wet locations.  Dry locations include roadsides and open fields.  

The common names all refer to the rattling sound made by the seeds inside the pod-like fruit when shaken.  It was first introduced into the US as a soil builder, its nitrogen fixing bacteria will improve the quality of the soil.  Its botanical name comes from an Ancient Greek word that translates to castanet, again referring to the sound the dried seeds make.  

Depending on its location, it grows as an annual or perennial herb.  It has alternate, simple, or divided leaves and yellow flowers on long terminal or axillary clusters, each being 5-parted and pea-like.  The fruit is an inflated, subcylindric pod with many seeds.

Native species include Crotalaria pumila and Crotalaria rotundifolia.

This plant serves as a host to the Swallowtail butterfly (Papilio glaucus), which is also referred to as a Tiger Butterfly.  

Insects, Diseases, and Other Plant Problems:  The seeds from this plant are toxic to livestock.  The self seeding by this plant can be weedy and aggressive in the surrounding locations.